It's an innocuous shipping container, no different than thousands of others moving every day across the globe. Traveling on a Taiwanese container ship across the Pacific, the box — designed as part of a global, commercial intermodal system and transported on ships, railroad cars and 18-wheel trucks — carries documentation saying it's filled with medical supplies from Indonesia. It might be loaded and unloaded onto several ships before it winds up on a dock in Baltimore, where an inspector looks over the documentation and sees nothing suspicious. The container becomes the load for a truck bound for Cincinnati, where it's delivered to a supply company that's a front for a terrorist organization.

http://www.armedforcesjournal.com/2006/12/2336959